Question

If \[\ce{C(s) + O2(g) -> CO2(g), \Delta H = - \text{x}}\]

\[\ce{CO(g) + \frac{1}{2} O2(g) -> CO2(g), \Delta H = - \text{y}}\],

Calculate Δ_f H for CO_(g) formation.

Options

• - Y - X

• Y - X

• X + Y

• X - Y

Answer 1

Y - X

Explanation:

\[\ce{C(s) + O2(g) -> CO2(g), \Delta H = - \text{x}}\]   .....(i)

\[\ce{CO(g) + \frac{1}{2} O2(g) -> CO2(g), \Delta H = - \text{y}}\]   ...(ii)

       \[\ce{C(s) + O2(g) -> CO2(g)}\]
\[\ce{CO(g) + \frac{1}{2} O2(g) -> CO2(g)}\]
(-)               (-)                     (-)       

\[\underline{\ce{C(s) + \frac{1}{2} O2(g) -> CO(g)}}\]

∴ Δ_r H for formation of CO = ΔH₁ - ΔH₂

= - x + y   or y - x